The present patent application claims priority from a German application Application No. 01100248.2, filed on Jan. 3, 2001.
1. Technical Field
The present invention relates to disk recycling in general, and in particular to a method for recycling a floppy disk having a layered structure on a glass substrate. Still more particularly, the present invention relates to a method for recycling a floppy disk having a layered structure on a glass substrate by removing the layered structure on the glass substrate.
2. Description of the Prior Art
Magnetic disks and photomagnetic disks are typically used as storage media for recording data processing information in computers. In recent years, substantial improvements have been made in the magnetic disk manufacturing by increasing the recording density while reducing the size and weight. For example, the diameters of magnetic disks have been reduced from 2.5 inches, to 1.8 inches and to 1.3 inches. Along with the diameter, the thickness of the disk substrate has also been reduced. Conventionally, an aluminum alloy has been used as the substrate material for magnetic disks. But in recent years, aluminum alloy has been replaced by glass that can provide smaller deformations, a more preferable flatness and better mechanical strengths.
Each year, billions upon billions of magnetic disks are fabricated. However, millions of the magnetic disks will have to be scrapped due to defects occurred during manufacture. More importantly, those scrapped magnetic disks cannot be easily and cost effectively recycled. For example, efforts to recycle scrapped magnetic disks have been made by immersing them in an acid solution, such as hydrochloric acid, to dissolve the layers present on the glass substrates. However, it has become apparent that the reaction time amounts to several hours, and what is even worse, the hydrochloric acid solution will attack the glass substrates and the chloride ions (Clxe2x88x92) also hold the danger of corroding the glass substrates. As a result, a substantial removal of the recycled substrate surface material is required, and the removal is done by a polishing process that removes several microns of the glass substrate material. Worse yet, the above-mentioned method of disk recycling allows only one single reuse because of the substrate thinning after the polishing process.
Under the prior art, a method for recycling disks, especially optical disks such as compact disks and digital video disks, having a layered structure with a reflective film and a dye layer, includes a step of retaining the disk in a liquid medium, a step of radiating ultrasonic waves onto the disk such that the substrate and the reflective film can separate from each other, and a step of bringing a solution into contact with the substrate separated from the reflective film such that the dye layer can be separated from the substrate in order to recover the substrate (the solution dissolves the dye layer). However, disadvantages of the above-mentioned method include high cost and the solution will attack the substrate to be recycled.
Consequently, it would be desirable to provide an improved method for recycling disks that is cost-effective and not harmful to glass substrates.
In accordance with a preferred embodiment of the present invention, a disk includes a layered structure on a glass substrate. Initially, the disk is exposed to gaseous sulphur dioxide in a humid environment. Then, the disk is treated with hot water to remove the layered structure from the glass substrate.
All objects, features, and advantages of the present invention will become apparent in the following detailed written description.